P-Hydroxycinnamaldehyde Induces B16-F1 Melanoma Cell Differentiation via the RhoA-MAPK Signaling Pathway.

BACKGROUND/AIMS: Due to its antitumor and gastroprotective properties, cochinchina momordica seed (CMS), has been widely used to treat cancer patients in Asia. Our previous reports have shown that CMS is able to induce the differentiation of B16-F1 melanoma cells. However, its functional component and mechanism remain unclear and are addressed in this study. METHODS AND RESULTS: CMSP (p-hydroxycinnamaldehyde isolated from CMS) inhibited the proliferation, migration and invasiveness of B16-F1 cells both in vivo and in vitro. CMSP also induced the differentiation of B16-F1 cells, as characterized by dendrite-like outgrowth, increased melanogenesis and enhanced tyrosinase activity. Furthermore, CMSP treatment reduced the level of malignant markers of melanoma, specifically S-100B and melanoma-derived growth regulatory protein precursor (MIA), in a concentration-dependent manner. According to a western blot analysis, B16-F1 cells treated with CMSP exhibited a sustained increase in p-P38 and decreased activities of ERK and JNK. Our data further indicated that the downregulation of GTP-RhoA, which was mediated by increased cAMP release, was involved in CMSP-induced changes in MAPK, while LPA (Lysophosphatidic acid) partially reversed CMSP-induced B16 cell differentiation. CONCLUSION: These results demonstrated that CMSP-induced differentiation of B16F1 cells may occur through the RhoA-MAPK axis, which suggests a new potential strategy for melanoma treatment.

Effect of nitric oxide on esophageal cancer cell line TE-1.

OBJECTIVE: To investigate the radiosensitizing effect of nitric oxide (NO) combined with radiation on esophageal cancer cell line TE-1. METHODS: Methyl thiazolyl tetrazolium (MTT) assay was used to assess the effects of NO and radiation on TE-1 cells regarding inhibition of cell proliferation. Flow cytometry was used to examine the effect of NO and radiation on cell apoptosis and cycle. Reverse transcription polymerase chine reaction and Western blot were used to evaluete the effect of NO on mRNA and protein expression of manganese superoxide dismutase (MnSOD). RESULTS: NO inhibited the proliferation of TE-1 cells while significantly enhancing their radiosensitivity. The application of NO combined with radiation significantly increased the apoptosis rate and G2/M phase proportion of TE-1 cells, with substantial decreases in the MnSOD mRNA and protein expression levels. CONCLUSIONS: NO reduces the MnSOD mRNA and protein expression levels by affecting TE-1 cell cycle, further inhibiting the apoptosis of esophageal cancer cells and enhancing the killing effect of radiation on esophageal cancer cells.

HIF-1α contributes to hypoxia-induced invasion and metastasis of esophageal carcinoma via inhibiting E-cadherin and promoting MMP-2 expression.

Hypoxia-inducible factor-1α (HIF-1α) has been found to enhance tumor invasion and metastasis, but no study has reported its action in esophageal carcinoma. The goal of this study was to explore the probable mechanism of HIF-1α in the invasion and metastasis of esophageal carcinoma Eca109 cells in vitro and in vivo. mRNA and protein expression of HIF-1α, E-cadherin and matrix metalloproteinase-2 (MMP-2) under hypoxia were detected by RT-PCR and Western blotting. The effects of silencing HIF-1α on E-cadherin, MMP-2 mRNA and protein expression under hypoxia or normoxia were detected by RT-PCR and Western blotting, respectively. The invasive ability of Eca109 cells was tested using a transwell chambers. We established an Eca109-implanted tumor model and observed tumor growth and lymph node metastasis. The expression of HIF-1α, E-cadherin and MMP-2 in xenograft tumors was detected by Western blotting. After exposure to hypoxia, HIF-1α protein was up-regulated, both mRNA and protein levels of E-cadherin were down-regulated and MMP-2 was up-regulated, while HIF-1α mRNA showed no significant change. SiRNA could block HIF-1α effectively, increase E-cadherin expression and inhibit MMP-2 expression. The number of invading cells decreased after HIF-1α was silenced. Meanwhile, the tumor volume was much smaller, and the metastatic rate of lymph nodes and the positive rate were lower in vivo. Our observations suggest that HIF-1α inhibition might be an effective strategy to weaken invasion and metastasis in the esophageal carcinoma Eca109 cell line.

[Bidirectional effect of MnSOD overexpression on the proliferation of esophageal cancer cells in vitro].

OBJECTIVE: To construct a recombinant lentiviral vector for manganese superoxide dismutase (MnSOD) gene expression, and observe its effect on the proliferation of esophageal cancer cells in vitro. METHODS: Chemical methods were employed for synthesis of the MnSOD cDNA sequence sections, along with the attB sites. Target gene fragment was constructed on the pMD-18T vector, and the recombinant plasmid pDONR221 was obtained after BP recombination reaction. Sequencing was followed by LR recombination reaction between the plasmid and DEST to obtain the lentiviral vector, which worked with helper plasmid for co-transfection of human embryonic kidney epithelial cells (293T cells). Amplification was done to determine its titer, and both transfection and selection procedures were made to get two stable transfected esophageal cancer TE-1 cell lines with medium MnSOD expression (TE-1Mm cells) and high MnSOD expression (TE-1Mh cell), and empty vector cell (TE-1Mn cells). Reverse transcription polymerase chine reaction (RT-PCR), immunofluorescence, immunocytochemistry and Western blot were used to detect the target gene with respect to its expression in the TE-1 cells. Additionally, colorimetric 3-[4,5-dimethy thiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, agar colony formation assay, annexin V-FITC/PI staining and flow cytometry experiments were also conducted as to observe the influence of the medium and high MnSOD overexpressions on the proliferation of esophageal cancer cells. RESULTS: RT-PCR indicated that the transfected TE-1 cells showed positive MnSOD expression at different levels. Immunofluorescence, immunocytochemistry and Western blot suggested that TE-1Mm cells and TE-1Mh cells had MnSOD protein expression at different levels. MTT assay indicated that TE-1Mm cells had a significantly decreased survival rate compared with that of the two control cells (TE-1 cells and TE-1Mn cells), and TE-1 Mh cells had an significantly increased survival rate (P<0.05). The colony formation ability of TE-1Mm cells was (23.0 +/- 2.7)%, and that of TE-1Mh cells was (45.3 +/- 4.5)%, significantly different form the (34.7 +/- 4.2)% in TE-1 cells and (33.7 +/- 4.7)% in TE-1Mn cells (P<0.05). Annexin V-FITC/PI double staining experiment of the stably transfected cells cultured for 48 h showed that the early apoptosis rate in TE-1Mm cells was (10.6 +/- 1.0)%, significantly higher than (2.6 +/- 0.2)% in the TE-1 cells, (2.5 +/- 0.6)% in the empty vector cells and (1.0 +/- 0.1)% in the TE-1Mh cels (P<0.05). The fluorescence index (FI) of mitochondrial apoptosis of TE-1Mm cells was 0.948 +/- 0.019, significantly lower than that of TE-1 cell (1.000 +/- 0.022) and empty vector The fluorescence index of TE-1Mn cells (0.997 +/- 0.023) and TE-1 cells (1.000 +/- 0.022) were significant different from that of 0.948 +/- 0.019 in TE-1Mm cells and 1.076 +/- 0.022 in TE-1Mh cells, indicating a significant difference of mitochondrial apoptosis between the cell groups. FCM results indicated that the ROS fluorescence index of TE-1Mm cells was 0.859 +/- 0.040, that of TE-1Mh cells was 0.763 +/- 0.039, significantly lower than that of TE-1 cells (1.000 +/- 0. 042) and empty vector cells (1.002 +/- 0.047) (P<0.05). CONCLUSIONS: Stably transfected cell lines with MnSOD expression have been successfully established. MnSOD overexpression shows bidirectional effect on the proliferation of esophageal cancer cells.

[Expression of MnSOD mRNA and protein in esophageal squamous cell carcinoma and its clinical significance].

OBJECTIVE: To investigate the expression of manganese superoxide dismutase (MnSOD) and to determine the relationship between MnSOD expression and clinicopathological features, biological behaviors in esophageal carcinoma. METHODS: Immunohistochemistry (SP) and RT-PCR were respectively used to detect the expression of MnSOD in 45 specimens of esophageal carcinoma tissues and normal esophageal mucosa (5 cm distant from the margin of cancer). RESULTS: The positive rate of MnSOD protein expression was 31.1% in esophageal carcinoma tissues, significantly lower than 86.7% in the normal tissues (P < 0.05). The expressions of MnSOD mRNA and protein were significantly correlated with the lesion length, depths of invasion and histological grade (P < 0.05), but not with lymph node metastasis, lesion site and gross type of the tumor (P > 0.05). The relative content of MnSOD mRNA was (0.310 ± 0.036) and (0.482 ± 0.053) in the cancer and normal tissues, respectively, with a significant difference between the two groups (P < 0.05). The relative content of MnSOD mRNA was significantly related to lesion length, depths of invasion and histological grade (P < 0.05), but not correlated with lymph node status, lesion site and gross type of the tumor (P > 0.05). CONCLUSION: The expression of MnSOD protein and mRNA is decreased in esophageal carcinoma, suggesting that MnSOD gene may be closely associated with the carcinogenesis and the degree of malignancy. Detection of MnSOD expression may be useful in diagnosis, treatment and prognosis of esophageal carcinoma.

Correction to: Promoter hypomethylation mediated upregulation of MicroRNA-10b-3p targets FOXO3 to promote the progression of esophageal squamous cell carcinoma (ESCC).

In the original publication of this manuscript [1], Fig. 6 contains a repeated image in error (the left image of 'Migration' and the left image of 'Invasion').

miR-4317 suppresses non-small cell lung cancer (NSCLC) by targeting fibroblast growth factor 9 (FGF9) and cyclin D2 (CCND2).

BACKGROUND: Non-small cell lung cancer (NSCLC) is a leading cause of death worldwide. MicroRNAs (miRNAs) have been indicated as crucial actors in cancer biology. Accumulating evidence suggests that miRNAs can be used as diagnostic and prognostic markers for NSCLC. METHODS: The purpose of this study was to characterize and identify the novel biomarker miR-4317 and its targets in NSCLC. The expression of miR-4317 was analyzed by in situ hybridization (ISH) and quantitative reverse transcription polymerase chain reaction (qRT-PCR). The effect of miR-4317 on proliferation was evaluated through 3-4,5-dimethylthiazol-2-yl-5-3-carboxymethoxyphenyl-2-4-sulfophenyl-2H-tetrazolium (MTS) and colony formation assays, and cell migration and invasion were evaluated through transwell assays. The expression of target proteins and downstream molecules was analyzed by qRT-PCR and western blot. Dual-luciferase reporter assay was used to assess the target genes of miR4317 in NSCLC cells. RESULTS: Our results demonstrated that miR-4317 was downregulated in NSCLC tissues and serum, particularly in lymph node metastasis and advanced clinical stage tissues. Kaplan-Meier survival analysis showed that NSCLC patients with high expression of miR-4317 exhibited better overall survival (OS). Enhanced expression of miR-4317 significantly inhibited proliferation, colony formation, migration and invasion, and hampered cycles of NSCLC cell lines in vitro. Our results suggested that miR-4317 functions by directly targeting fibroblast growth factor 9 (FGF9) and cyclin D2 (CCND2). In concordance with in vitro studies, mouse xenograft, lung, and brain metastatic studies validated that miR-4317 functions as a potent suppressor miRNA of NSCLC in vivo. Systemically delivered agomiR-4317 reduced tumor growth and inhibited FGF9 and CCND2 protein expression. Reintroduction of FGF9 and CCND2 attenuated miR-4317-mediated suppression of migration and invasion in NSCLC. CONCLUSIONS: Our results indicate that miR-4317 can reduce NSCLC cell growth and metastasis by targeting FGF9 and CCND2. These findings provide new evidence of miR-4317 as a potential non-invasive biomarker and therapeutic target for NSCLC.

Promoter hypomethylation mediated upregulation of MicroRNA-10b-3p targets FOXO3 to promote the progression of esophageal squamous cell carcinoma (ESCC).

BACKGROUND: Esophageal cancer is a high incident cancer worldwide with poor survival and limited therapeutic options. Alterations of microRNAs are common in cancers, and many of these micro RNAs are potential therapeutic and diagnostic targets to treat these cancers. miR-10b-3p located in chromosome region 2q31.1, and its expression is frequently increased in esophageal squamous cell carcinoma (ESCC). However, the biological functions, clinical significance and therapeutic implications of miR-10b-3p in ESCC remain unclear. METHODS: The expression levels of miR-10b-3p in ESCC specimens were analyzed by in situ hybridization (ISH) and quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays. Ectopic overexpression of miR-10b-3p in ESCC cells, mouse xenograft model, and metastasis model were used to evaluate the effects of miR-10b-3p on proliferation, and migration of cancer cells. Luciferase reporter assay and Western blot were performed to validate the potential targets of miR-10b-3p after the preliminary screening by computer-aided microarray analysis. RESULTS: We found that miR-10b-3p expression levels were significantly upregulated in the tumor tissues and serum samples of patients with ESCC. The expression levels of miR-10b-3p in both tumor tissues and serum samples were inversely associated with lymph node metastasis and clinical stages. We identified the expression level of miR-10b-3p in ESCC cancer samples as an independent prognostic marker of the overall survival rates of ESCC patients. We found more frequent hypomethylation of the CpG sites located upstream of the miR-10b-3p gene in the ESCC tissues compared with in the adjacent normal tissues, and the DNA methylation status of miR-10b-3p promoter region inversely correlated with the expression levels of miR-10b-3p. Ectopic overexpression of miR-10b-3p promoted cell proliferation, colony formation, migration and invasion in ESCC. While knockdown of miR-10b-3p had the opposite effects, particularly in promoting apoptosis. Mouse xenograft model confirmed that miR-10b-3p functions as a potent oncogenic miRNA in ESCC, which also promoting ESCC metastasis. Mechanistically, we found miR-10b-3p regulated FOXO3 expression by directly binding to the 3'-untranslated region. And systemic delivery of miR-10b-3p antagomir reduced tumor growth and inhibit FOXO3 protein expression in nude mice. CONCLUSIONS: Collectively, our findings suggested upregulated expression of miR-10b-3p caused by promoter hypomethylation contributed to the progression of ESCC; Thus, miR-10b-3p is a potentially effective biomarker for ESCC that could have further therapeutic implications.

Epithelial membrane protein 1 negatively regulates cell growth and metastasis in colorectal carcinoma.

AIM: To determine the expression and function of epithelial membrane protein 1 (EMP1) in colorectal carcinoma. METHODS: Colorectal samples were taken from cancer lesions and adjacent normal tissue in colorectal cancer patients immediately after endoscopic biopsy. A portion of the sample was either fixed in 4% paraformaldehyde and embedded in paraffin for immunohistochemistry or stored in liquid nitrogen for Western blot. In order to determine protein expression of EMP1 in colorectal cancer (n = 63) and normal tissue (n = 31), semi-quantitative immunohistochemistry and Western blot were utilized. For in vitro studies, the human colorectal cancer cell line SW-480 was maintained in RPMI-1640 medium supplemented with 10% fetal bovine serum. Recombinant lentivirus mediated overexpression of EMP1 in SW-480 cells was quantified by real-time reverse transcription-polymerase chain reaction and Western blot. Control SW-480 cells were transfected with an empty vector. To further study the effect of EMP1 overexpression in SW-480 cells, cell proliferation, apoptosis, migration and invasion assays were conducted. RESULTS: Expression of EMP1 was significantly lower in colorectal cancer tissue than in normal tissue using both immunohistochemistry (39.7% vs 90.3% of tissues, P < 0.05) and Western blot (0.126 ± 0.022 vs 0.632 ± 0.053, P < 0.05). The level of EMP1 protein expression was not correlated with gender, age, or tumor location. Decreased expression of EMP1 was significantly correlated with T stage, lymph node metastasis, clinic stage, and histological grade in patients with colorectal cancer (P < 0.05). According to Kaplan-Meier analysis, low EMP1 expression correlated significantly with poor overall five-year survival (34.2% vs 64.0% survival, P < 0.05). SW-480 cells transfected with EMP1 had a lower survival fraction, higher cell apoptosis (12.1% ± 1.3% vs 3.1% ± 0.6%, P < 0.05), a significant decrease in migration and invasion (124.0 ± 17.0 and 87.0 ± 12.0, respectively vs 213.0 ± 29.0 and 178.0 ± 21.0, respectively, P < 0.05), higher caspase-9 (0.635 ± 0.063 vs 0.315 ± 0.032, P < 0.05), and lower VEGFC protein expression (0.229 ± 0.021 vs 0.519 ± 0.055, P < 0.05) relative to cells not transfected with EMP1. CONCLUSION: Low EMP1 expression in colorectal cancer is associated with increased disease severity, suggesting that EMP1 may be a negative regulator of colorectal cancer.

Interactions between filamin A and MMP-9 regulate proliferation and invasion in renal cell carcinoma.

This study aimed to analyze the expression, clinical significance of filamin A (FLNA) in renal cell carcinoma (RCC) and biological effects in a cell line by regulating FLNA expression. Immunohistochemistry and Western blotting were used to analyze FLNA protein expression in 70 cases of RCC and normal tissues to study the relationship with clinical factors. FLNA lentiviral and empty vectors were transfected into RCC to study the influence of up-regulated expression of FLNA. FLNA siRNA was transiently transfected into ACHN kidney carcinoma cells by a liposome-mediated method and protein was detected by Western blotting. The level of expression was found to be significantly lower in RCC than normal tissues (p<0.05). No correlation was noted with gender, age, tumor size or pathological types (p>0.05), but links with lymph node metastasis, clinic stage and histological grade were noted (p<0.05). Loss of FLNA expression correlated significantly with poor overall survival time by Kaplan-Meier analysis (p<0.05). Results for biological function showed that ACHN cells transfected with FLNA had a lower survival fraction, significant decrease in migration and invasion, higher cell apoptosis, higher percentage of the G0/G1 phases, and lower MMP-9 protein expression compared with ACHN cells untransfected with FLNA (p<0.05). However, renal 786-0 cells transfected with FLNA siRNA had a higher survival fraction, significant increase in migration and invasion, and higher MMP-9 protein expression compared (p<0.05). In conclusion, FLNA expression was decreased in RCC and correlated significantly with lymph node metastasis, clinic stage, histological grade and poor overall survival, suggesting that FLNA may play important roles as a a tumor suppressor in RCC by promoting degradation of MMP-9.

Different association of manganese superoxide dismutase gene polymorphisms with risk of prostate, esophageal, and lung cancers: evidence from a meta-analysis of 20,025 subjects.

Altered expression or function of manganese superoxide dismutase (MnSOD) has been shown to be associated with cancer risk but assessment of gene polymorphisms has resulted in inconclusive data. Here a search of published data was made and 22 studies were recruited, covering 20,025 case and control subjects, for meta- analyses of the association of MnSOD polymorphisms with the risk of prostate, esophageal, and lung cancers. The data on 12 studies of prostate cancer (including 4,182 cases and 6,885 controls) showed a statistically significant association with the risk of development in co-dominant models and dominant models, but not in the recessive model. Subgroup analysis showed there was no statistically significant association of MnSOD polymorphisms with aggressive or nonaggressive prostate cancer in different genetic models. In addition, the data on four studies of esophageal cancer containing 620 cases and 909 controls showed a statistically significant association between MnSOD polymorphisms and risk in all comparison models. In contrast, the data on six studies of lung cancer with 3,375 cases and 4,050 controls showed that MnSOD polymorphisms were significantly associated with the decreased risk of lung cancer in the homozygote and dominant models, but not the heterozygote model. A subgroup analysis of the combination of MnSOD polymorphisms with tobacco smokers did not show any significant association with lung cancer risk, histological type, or clinical stage of lung cancer. The data from the current study indicated that the Ala allele MnSOD polymorphism is associated with increased risk of prostate and esophageal cancers, but with decreased risk of lung cancer. The underlying molecular mechanisms warrant further investigation.

Characteristics of recurrence after radical esophagectomy with two-field lymph node dissection for thoracic esophageal cancer.

Postoperative radiotherapy has shown positive efficacy in lowering the recurrence rate and improving the survival rate in cases involving lymph node (LN) metastasis. However, the radiotherapy target volume remains controversial. Certain published studies have paid more attention to LNs found to be affected during surgery, while little effort has been made to study the LN metastatic pattern following surgery and its influence on the determination of the target volume of postoperative radiotherapy. In this study, the locoregional recurrence of esophageal squamous cell cancer was examined in 134 patients receiving radical surgery with two-field lymph node dissection from 2004 to 2009. In the 134 cases of recurrence, LN metastasis occurred in 126 patients (94.0%) while 13 patients (9.7%) developed anastomotic recurrence and 5 patients (3.7%) experienced tumor bed recurrence. The difference among the groups was statistically significant (P= 0.000). In the 126 cases with lymph node metastasis, the mediastinal metastasis rate (80.2%) was significantly higher compared with the rate of supraclavicular metastasis and abdominal metastasis (P= 0.000). A significant difference was identified between right and left supraclavicular LN metastasis (31.7% vs 16.7%, P= 0.005). Furthermore, the difference between the metastatic rates in the upper (73.8%), middle (39.7%) and lower mediastinum (1.6%) was statistically significant (P=0.000). Nevertheless, no significant correlation between the rate of LN metastasis was observed in the supraclavicular, mediastinal and abdominal regions for upper, middle and lower thoracic carcinomas (P= 0.404, P= 0.718 and P= 0.169, respectively). Based on our data, LN metastasis is the major locoregional recurrence pattern for esophageal squamous cell cancer following radical surgery. The high-risk lymphatic drainage areas include the supraclavicular nodes, recurrent laryngeal nerve nodes, azygos nodes and subcarinal nodes.

[Effect of HIF-1α and its mechanism on invasion and metastasis of esophageal carcinoma Eca109 cells in vitro and in vivo].

AIM: To investigate the effects of HIF-1α by RNAi on invasion and metastasis of esophageal carcinoma Eca109 cells in vitro and in vivo, in order to explore its probable mechanism. METHODS: CoCl(2); was used to mimic tumor hypoxic microenvironment. mRNA and protein levels of HIF-1α, E-cadherin and MMP-2 under hypoxia were detected by RT-PCR and immunohistochemistry. The effects of silencing HIF-1α by RNAi on HIF-1α, E-cadherin and MMP-2 mRNA were detected by RT-PCR. The effect of RNAi on invasion and metastasis were tested by cell scratch assay and transwell chambers. The Eca109-implanted nude mouse model was established, and the effects of HIF-1αon tumor growth and lymphoid node metastasis were observed. The expressions of HIF-1α, E-cadherin and MMP-2 in transplanted tumors were detected by Western blot, and the effects of HIF-1α on tumor growth, invasion and metastasis in vitro and in vivo were analyzed. RESULTS: Hypoxia up-regulated HIF-1α protein, mRNA and protein levels of E-cadherin down-regulated, and MMP-2 up-regulated, while had no effect on HIF-1α mRNA . RNAi could silencing HIF-1α effectively, and inhibited E-cadherin or MMP-2 decreased or increased, respectively. The migration and the number of invading cells decreased (P<0.05) after silencing HIF-1α by RNAi. The tumor volume was much smaller, lymph node metastasis rate lower as well in vivo (P<0.05). CONCLUSION: Via its effects on E-cadherin and MMP-2, HIF-1α regulate the growth, invasion and metastasis of Eca109 cells in vitro and in vivo.

Bidirectional regulation of manganese superoxide dismutase (MnSOD) on the radiosensitivity of esophageal cancer cells.

The mitochondrial antioxidant protein manganese superoxide dismutase (MnSOD) may represent a new type of tumor suppressor protein. Overexpression of the cDNA of this gene by plasmid or recombinant lentiviral transfection in various types of cancer leads to growth suppression both in vitro and in vivo. We previously determined that changes in MnSOD expression had bidirectional effects on adriamycin (ADR) when combined with nitric oxide (NO). Radiation induces free radicals in a manner similar to ADR, so we speculated that MnSOD combined with NO would also have a bidirectional effect on cellular radiosensitivity. To examine this hypothesis, TE-1 human esophageal squamous carcinoma cells were stably transfected using lipofectamine with a pLenti6-DEST plasmid containing human MnSOD cDNA at moderate to high overexpression levels or with no MnSOD insert. Blastidicin-resistant colonies were isolated, grown, and maintained in culture. We found that moderate overexpression of MnSOD decreased growth rates, plating efficiency, and increased apoptosis. However, high overexpression increased growth rates, plating efficiency, and decreased apoptosis. When combined with NO, moderate overexpression of MnSOD increased the radiosensitivity of esophageal cancer cells, whereas high MnSOD overexpression had the opposite effect. This finding suggests a potential new method to kill certain radioresistant tumors and to provide radioresistance to normal cells.